Heart disease (HD) remains a leading cause of morbidity and mortality despite recent advances in pharmacotherapy and improved care. Mounting prevalence of risk factors such as hypertension, obesity, and diabetes, coupled with genetic factors and smoking, have all contributed to perturbation of vascular mechanisms leading to coronary endothelial and vascular smooth muscle cell dysfunction, intimal thickening, plaque formation, vascular and cardiac remodeling, myocardial infarction, hypertrophy, and heart failure. It has been proposed that an imbalance between vasoconstrictive and vasodialator mechanisms initiated by coronary endothelial dysfunction plays a critical role in the inducing cascade of signaling events leading to pathophysiology associated with HD. Based on four years of our investigation, our preliminary data, and evidence from literature, we propose that a balance between endothelial angiotensin converting enzyme (ACE) and ACE2 is critical in maintaining normal cardiac homeostasis. Thus, an imbalance in ACE/ACE2 is central in the initiation of pathophysiological events leading to HD. We hypothesize that increasing levels of cardiac ACE2 or its product, Angiotensin-(1-7) [Ang-(1-7)], would increase coronary neovascularization, decrease cardiac remodeling, and improve cardiac function to ameliorate and reverse HD. We propose the following specific aims to support or refute this hypothesis: Aim 1 is proposed to investigate the beneficial effects of a novel and newly discovered ACE2 activator, Diminazene Aceturate (DIZE), on cardiac pathophysiology and elucidate its mechanism of action. Aim 2 will test the hypothesis that local delivery of ACE2 or Ang-(1-7) by bone marrow-derived progenitor cells (BMPCs) will reverse cardiac pathophysiology. Aim 3 will investigate the hypothesis that local delivery of ACE2 or Ang-(1-7) by human BMPCs and cardiac progenitor cells will reverse cardiac dysfunctions in immune-deficient SCID rats. This multidisciplinary, integrative, and translational approach to investigate the hypothesis that endothelial ACE/ACE2 is critical in HD pathophysiology is technically and conceptually innovative. Thus, the proposed study will: (i) provide experimental evidence for our hypothesis, (ii) establish mechanisms by which ACE2/Ang- (1-7) axis of the renin-angiotensin system produces cardiovascular protective effects, (iii) backward- translational studies will identify dysfunctional mechanisms in cardiovascular-relevant progenitor cells from HD patients, and (iv) put us in an outstanding position to transition into clinical phase to test both DIZE and genetically-modified cell based therapy for HD. Finally, we believe that the outcome of our investigation will have an immediate impact in providing cardioprotection in patients undergoing anthracyclin chemotherapy. PUBLIC HEALTH RELEVANCE: Endothelial dysfunction is one of the early cellular events in the development and establishment of cardiovascular diseases leading to devastating outcomes such as coronary artery disease, thrombosis, myocardial infarction, hypertrophy, and heart failure. The overall objective of our investigation is to test a novel and innovative hypothesis that an imbalance in the vasodeleterious axis (ACE/Ang II/AT1R) and vasoprotective axis (ACE2/Ang-(1-7)/MasR) of the renin-angiotensin system initiates a cascade of signaling events that result in endothelial dysfunction and lead to heart disease. Thus, we propose that restoring this imbalance by a novel ACE2 activator or by genetically-modified stem cells to deliver ACE2 or Ang-(1-7) to the site of cardiac injury, would increase vasculogenesis, and protect and regenerate cardiac myocytes leading to a long-term beneficial outcome in HD. Finally, we believe that ACE2/Ang-(1-7) based concept will have an immediate impact not only in HD therapeutics, but will lead to the development of novel cardioprotective strategies in patients undergoing anthracyclin chemotherapy.